High strain point alkali free alumino-silicate glasses, such as, glasses for ultra high resolution Liquid Crystal Display (LCD) substrates using amorphous silicon or oxide thin film transistors (TFTs), or glasses for organic light emitting diode (OLED) substrates using low temperature polysilicon (LTPS) TFT deposition have been designed to allow high temperature processing of the TFT (up to 700° C.) while not suffering from deformation. These glasses can be formed using a fusion draw process where liquid glass flows over the lips of a glass overflow forming block made of zircon (ZrSiO4) material and fuses at the bottom of the glass overflow forming block to form a sheet. Zircon forming blocks that come in contact with alkali free alumino-boro-silicate glasses offer good corrosion resistance and mechanical properties at the forming temperature of glass. However, the forming of these higher strain point alkali free alumino-silicate glasses is more demanding on the forming blocks because of the higher forming temperature (between +30 and 120° C.). The higher forming temperature can increase the rate of reaction between the glass and the zircon materials leading to higher formation of bubbles in the glass with current zircon materials which is not acceptable for the ultra high resolution TFT substrate applications. Secondly, the higher forming temperature activates the creep deformation rate of the zircon material leading to higher sag of the forming blocks (up to 10 times more deformation) that is not acceptable for the forming of these glasses. There's therefore a need for a new range of zircon materials with improved properties at high temperatures.